Abstract:

A perpendicular magnetic recording layer may include a hard granular
layer, an exchange break layer formed on the hard granular layer, and a
soft granular layer formed on the exchange break layer. In some
embodiments, the exchange break layer may consist essentially of
ruthenium. In some embodiments, the perpendicular magnetic recording
layer may include n magnetic layers and n-1 exchange break layers, where
n is greater than or equal to three, and where the n-1 exchange break
layers alternate with the n magnetic layers in the magnetic recording
layer.

2. The apparatus of claim 1, wherein the exchange break layer comprises a
thickness of less than about 3 angstroms.

3. The apparatus of claim 1, wherein the exchange break layer comprises a
thickness of about 2 angstroms.

4. The apparatus of claim 1, wherein a magnetic anisotropy of the soft
granular layer is lower than a magnetic anisotropy of the hard granular
layer.

5. The apparatus of claim 1, further comprising a continuous granular
composite layer formed on the soft granular layer.

6. The apparatus of claim 5, wherein the exchange break layer comprises a
first exchange break layer, further comprising a second exchange break
layer formed on the soft granular layer, and wherein the continuous
granular composite layer is formed on the second exchange break layer.

8. The apparatus of claim 7, wherein the n magnetic layers comprise a hard
granular layer, a soft granular layer, and a continuous granular
composite layer, wherein the n-1 exchange break layers comprise a first
exchange break layer and a second exchange break layer, and wherein the
first exchange break layer is formed on the hard granular layer, the soft
granular layer is formed on the first exchange break layer, the second
exchange break layer is formed on the soft granular layer, and the
continuous granular composite layer is formed on the second exchange
break layer.

9. The apparatus of claim 8, wherein a magnetic anisotropy of the soft
granular layer is lower than a magnetic anisotropy of the hard granular
layer, and wherein a magnetic anisotropy of the continuous granular
composite layer is lower than the magnetic anisotropy of the soft
granular layer.

10. The apparatus of claim 7, wherein the n magnetic layers comprise a
hard granular layer, an intermediate granular layer, and a soft granular
layer, wherein the n-1 exchange break layers comprise a first exchange
break layer and a second exchange break layer, and wherein the first
exchange break layer is formed on the hard granular layer, the
intermediate granular layer is formed on the first exchange break layer,
the second exchange break layer is formed on the intermediate granular
layer, and the soft granular layer is formed on the second exchange break
layer.

11. The apparatus of claim 10, wherein a magnetic anisotropy of the soft
granular layer is lower than a magnetic anisotropy of the intermediate
granular layer, and wherein a magnetic anisotropy of the intermediate
granular layer is lower than the magnetic anisotropy of the hard granular
layer.

12. The apparatus of claim 10, further comprising a continuous granular
composite layer formed on the soft granular layer.

13. The apparatus of claim 7, further comprising a continuous granular
composite layer formed on the nth magnetic layer.

14. The apparatus of claim 7, wherein a first of the n-1 exchange break
layers consists essentially of ruthenium.

15. The apparatus of claim 7, wherein a first of the n-1 exchange break
layers comprises a thickness of less than about 3 angstroms.

16. The apparatus of claim 15, wherein a first of the n-1 exchange break
layers comprises a thickness of about 2 angstroms.

17. The apparatus of claim 7, wherein a second of the n-1 exchange break
layers consists essentially of ruthenium.

18. The apparatus of claim 7, wherein a second exchange break layer of the
n-1 exchange break layers comprises at least one of a CoCr alloy, a CoRu
alloy, or a CoCrRu alloy.

20. The method of claim 19, wherein the exchange break layer comprises a
first exchange break layer, and further comprising:forming a second
exchange break layer on the soft granular layer; andforming a continuous
granular composite layer on the second exchange break layer.

[0002]In one aspect, the disclosure is directed to an apparatus comprising
a hard granular layer, an exchange break layer formed on the hard
granular layer, and a soft granular layer formed on the exchange break
layer. According to this aspect of the disclosure, the exchange break
layer consists essentially of ruthenium.

[0003]The details of one or more embodiments of the invention are set
forth in the accompanying drawings and the description below. These and
various other features and advantages will be apparent from a reading of
the following detailed description.

BRIEF DESCRIPTION OF DRAWINGS

[0004]FIG. 1 is a schematic diagram of an example of a hard disc drive.

[0005]FIG. 2 is a schematic block diagram illustrating an example of a
magnetic recording medium including a recording layer comprising a hard
granular layer, an exchange break layer, a soft granular layer, and a
continuous granular composite layer.

[0006]FIG. 3 is a schematic block diagram illustrating an example of a
magnetic recording medium including a recording layer comprising a hard
granular layer, a first exchange break layer, a soft granular layer, a
second exchange break layer, and a continuous granular composite layer.

[0009]FIG. 6 is a diagram of remnant coercivity versus applied magnetic
field angle for three magnetic recording layer stacks.

[0010]FIG. 7 is a diagram of normalized remnant coercivity versus applied
magnetic field angle for three magnetic recording layer stacks.

[0011]FIG. 8 is a scatter diagram of a measure of thermal stability versus
exchange break layer thickness for a recording layer including a
ruthenium exchange break layer.

[0012]FIG. 9 is a scatter diagram of switching field distribution as a
function of breaklayer thickness for a series of examples of magnetic
recording layers including an exchange break layer.

[0013]FIG. 10 is a diagram illustrating a comparison of remnant coercivity
versus exchange break layer thickness for two recording layer stacks, one
of which includes a soft granular layer and one of which does not
includes a soft granular layer.

[0014]FIG. 11 is a diagram illustrating a comparison of normalized remnant
coercivity versus exchange break layer thickness for two recording layer
stacks, one of which includes a soft granular layer and one of which does
not includes a soft granular layer.

[0015]FIG. 12 is a diagram illustrating estimated achievable areal density
for a series of recording layers including exchange break layers of
various thicknesses.

[0016]FIG. 13 is a schematic block diagram illustrating an example of a
magnetic recording medium including a recording layer comprising a hard
granular layer, a first exchange break layer, an intermediate granular
layer, a second exchange break layer, a soft granular layer, a third
exchange break layer, and a continuous granular composite layer.

[0018]FIG. 15 is diagram of normalized remnant coercivity versus applied
magnetic field angle for a recording medium including a 5-layer recording
layer and a recording medium including a 7-layer recording layer.

DETAILED DESCRIPTION

[0019]A perpendicular magnetic recording system consists primarily of a
magnetic recording and read head flying above a rotating magnetic data
storage medium, on which a magnetic recording layer is deposited. The
magnetic recording layer may include a plurality of grains having a
random granular structure. By energizing the recording component of the
recording and read head, a magnetic field is produced that induces the
magnetization of grains to point either up or down, depending on the
magnetization direction of the applied field. During the read process,
the read portion of the recording and read head senses the magnetic flux
generated by the oriented magnetic grains and interprets the magnetic
flux as data.

[0020]Progress in magnetic data storage comes primarily through increasing
the storage capacity of the medium, which may be accomplished by
increasing the areal density of the magnetic recording layer (commonly
expressed as Gigabit per square inch (Gb/in2). Magnetic data storage
media with a smaller average grain diameter may allow storing the same
amount of data in a smaller area. However, magnetic stability of the
storage media becomes a greater concern as the storage density increases.
The grains maintain their magnetization orientation due to magnetic
anisotropy energy of the grains, which is proportional to the grain
volume. The anisotropy energy competes with thermal energy fluctuations,
which would orient the magnetization of the grains randomly, such that
data storage is hindered. Thermal fluctuation energy depends only on
temperature. The ratio of magnetic anisotropy energy to thermal
fluctuation energy is called the energy barrier, and is a measure of the
magnetic stability of the grain magnetization. The energy barrier is
proportional to the volume of the grain. Reducing an average grain
diameter (and thus volume) increases areal density but reduces magnetic
stability.

[0021]To mitigate the reduction in magnetic stability, the average
magnetic anisotropy energy of the grains can be increased. However,
increasing the average magnetic anisotropy energy of the grains also
increases a magnetic field required to change the magnetic orientation of
the grains during the data recording process. Currently, the magnetic
field the recording head is able to produce is limited by the saturation
moment of the magnetic material at a tip of the recording head, and is
also decreased substantially from a maximum value due to separation
between the recording head and the magnetic recording layer.

[0022]Some perpendicular media have at the bottom of the magnetic
recording layer a granular CoCrPt alloy layer, with lateral magnetic
decoupling among the magnetic grains provided by a non-magnetic oxide
(SiO2 or TiO2). This granular CoCrPt-alloy layer has high
magnetic anisotropy, which provides magnetic stability. An M-H
(magnetization-coercivity) loop of a magnetic storage medium consisting
of only this layer will have a considerable slope due to demagnetizing
interactions (fields) among adjacent grains. In a collection of grains
under influence of demagnetizing interactions only, the magnetization
orientation of the grains points randomly up and down. During a magnetic
data recording process, the grains experience both an external field
applied by the recording head and this demagnetizing field; thus, the
applied field necessary to change magnetic orientation of the grains of
the magnetic recording layer has a wide distribution, leading to
recording poor performance.

[0023]In some magnetic storage media, the demagnetizing field effects are
compensated for by a continuous magnetic layer, referred to as a
continuous granular composite (CGC) layer, overlying the granular CoCrPt
alloy layer, which provides lateral exchange interaction among the grains
of the granular CoCrPt alloy layer. A magnetic storage medium including
such a recording layer structure may be referred to as a continuous
granular composite (CGC) medium. The lateral magnetic exchange
interaction facilitates alignment of neighboring grains in the same
magnetization orientation. Uniformity of lateral magnetic exchange
interaction among the grains is important for good recording performance.
The CGC layer typically has relatively less anisotropy energy than the
granular CoCrPt alloy layer.

[0024]Besides controlling the exchange between the grains of the granular
CoCrPt alloy layer, the addition of the CGC layer also decreases the
average coercivity of the magnetic recording layer. In this magnetic
recording layer, adding greater or lesser amounts of lateral exchange
coupling controls the switching field of the medium. Usually, a thicker
continuous magnetic layer leads simultaneously to more lateral exchange
interaction and to a lower switching field. Increasing the lateral
magnetic exchange beyond the value required to balance the demagnetizing
field interactions may increase an effective magnetic grain size, due to
clustering of adjacent grains due to lateral magnetic exchange. Thus,
improvement of media write-ability through lateral magnetic exchange
coupling is limited.

[0025]Even though a magnetic recording layer of a CGC medium is a stack
composed of at least two layers, the switching of the magnetization
orientation of the recording layer is coherent. In other words, all of
the layers in the magnetic recording layer of a CGC medium switch
substantially simultaneously. When a write field is applied at various
angles with respect to the perpendicular direction, the switching field
value has a minimum at about 45 degrees, and a maximum at about 0 and
about 90 degrees. This is called the Stoner-Wohlfarth curve and all CGC
media follow it, which indicates the coherent magnetization orientation
switching of the CGC magnetic recording layer.

[0026]In the current disclosure, the magnetic recording layer structure
itself allows for self-assist in the writing process. In other words, the
magnetic recording layers proposed herein may have a high energy barrier,
while facilitating a switching field that is used to switch the
magnetization of the grains that is equal to or even less than the
switching field of some media, such as CGC media.

[0027]The current disclosure describes a magnetic recording layer
including at least two granular magnetic layers. The magnetic recording
layer may include a soft granular layer formed over a hard granular
layer. The soft granular layer has a magnetic anisotropy value that is
less than the magnetic anisotropy value of the hard granular layer. The
hard and soft granular layers are vertically exchange coupled, so that
each magnetic grain has a magnetically soft (lower magnetic anisotropy)
top and a magnetically hard (higher magnetic anisotropy) bottom. When an
external magnetic field is applied to a grain, magnetic orientation of
the soft portion and the hard portion switch non-coherently. In
non-coherent switching, the magnetic orientation of the soft portion of
the grain begins rotating before magnetic orientation of the hard portion
of the grain, since the soft portion has lower magnetic anisotropy that
the hard portion. Due to the vertical exchange coupling, the magnetic
moment of the soft portion will exercise a magnetic torque on the
magnetic moment of the hard portion, assisting with switching of the
magnetic orientation of the hard portion. Deviations from the
Stoner-Wolfarth curve of the remnant coercivity versus applied field
angle can identify this non-coherent switching mechanism.

[0028]The magnetic anisotropy energy of the composite grain may be stored
largely in the hard layer. By adding the soft layer, the average magnetic
anisotropy field of the composite structure will decrease by virtue of
averaging. An exchange coupled composite (ECC) effect consists of
obtaining a switching field (coercivity) for the grains that is smaller
than the value expected from the average of the magnetic anisotropies of
the hard granular layer and the soft granular layer.

[0029]FIG. 1 illustrates an exemplary magnetic disc drive 10 including a
magnetic recording and read head according to one aspect of the present
disclosure. Disc drive 10 includes base 12 and top cover 14, shown
partially cut away. Base 12 combines with top cover 14 to form the
housing 16 of disc drive 10. Disc drive 10 also includes one or more
rotatable magnetic data storage media 18. Magnetic data storage media 18
are attached to spindle 24, which operates to rotate media 18 about a
central axis. Magnetic recording and read head 22 is adjacent to magnetic
data storage media 18. Actuator arm 20 carries magnetic recording and
read head 22 for communication with each of magnetic data storage media
18.

[0030]Magnetic data storage media 18 store information as magnetically
oriented bits on a magnetic recording layer. Magnetic recording and read
head 22 includes a recording (write) head that generates a magnetic field
sufficient to magnetize discrete domains of the magnetic recording layer
on magnetic data storage media 18. These discrete domains of the magnetic
recording layer each represent a bit of data, with one magnetic
orientation representing a "0" and a substantially opposite magnetic
orientation representing a "1." Magnetic recording and read head 22 also
includes a read head that is capable of detecting the magnetic fields of
the discrete magnetic domains of the magnetic recording layer.

[0031]Magnetic data storage media 18 may include a composite magnetic
recording layer structure, which is described herein. Some embodiments of
the magnetic recording layer may include a top, magnetically soft layer
deposited directly on a bottom, magnetically hard layer. As described
above, in order to achieve the ECC effect, magnetic orientation switching
of the soft layer and the hard layer should be non-coherent. In an ECC
magnetic recording layer exhibiting non-coherent magnetic orientation
switching, the magnetic orientation of the soft layer begins switching at
an applied magnetic field value below an average magnetic anisotropy of
the magnetic recording layer (i.e., the average magnetic anisotropy of
the soft layer and the hard layer). The nucleation field, which is the
magnetic field at which switching of the soft layer begins, depends on
the exchange stiffness of the soft layer. The exchange stiffness of the
soft layer is a measure of how tightly magnetically coupled the soft
layer is to the hard layer, and is inversely proportional to the
thickness of the soft layer. In recording media, the total magnetic
recording layer thickness may be less than approximately 20 nanometers
(nm). The soft layer may be thinner than 13 nm and consequently the
nucleation field may be prohibitively high. One solution, which may
reduce the nucleation field, is the introduction of an exchange break
layer between the hard magnetic layer and the soft magnetic layer.

[0032]The exchange break layer may affect the vertical exchange coupling
between the top, magnetically soft layer and the bottom, magnetically
hard layer, so that the nucleation field required to nucleate switching
in the soft part is not prohibitively high, but at the same time, the
soft layer is able to exercise a magnetic torque on the hard layer. Thus,
the exchange break layer may reduce the overall coercivity of the
magnetic recording layer and facilitate recording of data to the magnetic
recording layer.

[0034]Substrate 32 may include any material that is suitable to be used in
magnetic recording media, including, for example, Al, NiP plated Al,
glass, ceramic glass, or the like.

[0035]Although not shown in FIG. 2, in some embodiments, an additional
underlayer may be present immediately on top of substrate 32. The
additional underlayer may be amorphous and provides adhesion to the
substrate and low surface roughness.

[0036]A soft underlayer (SUL) 34 is formed on substrate 32 (or the
additional underlayer, if one is present). SUL 34 may be any soft
magnetic material with sufficient saturation magnetization (Bs) and
low magnetic anisotropy (Hk). For example, SUL 34 may be an
amorphous soft magnetic material such as Ni; Co; Fe; an Fe-containing
alloy such as NiFe (Permalloy), FeSiAl, FeSiAlN, or the like; a
Co-containing allow such as CoZr, CoZrCr, CoZrNb, or the like; or a
CoFe-containing alloy such as CoFeZrNb, CoFe, FeCoB, FeCoC, or the like.

[0037]First interlayer 36 and second interlayer 38 may be used to
establish an HCP (hexagonal close packed) crystalline orientation that
induces HCP (0002) growth of the hard granular layer 42, with a magnetic
easy axis perpendicular to the film plane.

[0038]Perpendicular recording layer 40 may be formed on second interlayer
38, and includes hard granular layer 42, exchange break layer 44, soft
granular layer 46, and CGC layer 48. Hard granular layer 42 may have a
higher magnetic anisotropy than soft granular layer 46. The magnetic
anisotropies of hard granular layer 42 and soft granular layer 46 may
each be oriented in a direction substantially perpendicular to the plane
of recording layer 40 (e.g., the easy axes of hard granular layer 42 and
soft granular layer 46 may each be substantially perpendicular to the
plane of recording layer 40). Exchange break layer 44 may be used to
adjust the vertical exchange coupling between hard granular layer 42 and
soft granular layer 46.

[0039]In some embodiments, each of hard granular layer 42 and soft
granular layer 46 may include Co alloys. For example, the Co alloy may
include Co in combination with at least one of Cr, Ni, Pt, Ta, B, Nb, O,
Ti, Si, Mo, Cu, Ag, Ge, or Fe. The compositions of hard granular layer 42
and soft granular layer 46 may be the same, or may be different. For
example, soft granular layer 46 may include a lower percentage of Pt than
hard granular layer 42. In some embodiments, at least one of hard
granular layer 42 and soft granular layer 46 may include an Fe--Pt alloy,
a Sm--Co alloy, or the like. In some embodiments, hard granular layer 42
and/or soft granular layer 46 may include a non-magnetic oxide, such as
SiO2, TiO2 CoO, Cr2O3, Ta2O5, or the like,
which separates the magnetic grains within the respective layer. In one
example, hard granular layer 42 includes a CoCrPt alloy, at least one
oxide, and a dopant element, such as Ru, W, Nb, or the like. In one
example, soft granular layer 46 includes a CoCrPt alloy, at least one
oxide, and a dopant element, such as Ru, W, Nb, or the like. Soft
granular layer 42 may include less Pt than hard granular layer 46.

[0040]In some embodiments, hard granular layer 42 may have a thickness
between approximately 50 Angstroms (Å) and approximately 150 Å.
In one embodiment, hard granular layer 42 may have a thickness of
approximately 90 Å. In some embodiments, soft granular layer 46 may
have a thickness between approximately 20 Å and approximately 100
Å. In one embodiment, soft granular layer 46 may have a thickness of
approximately 40 Å. Of course, other thicknesses for hard granular
layer 42 and soft granular layer 46 are also contemplated.

[0041]A protective overcoat 50, such as, for example, diamond like carbon,
may be formed over recording layer 40. In other examples, protective
overcoat 50 may include, for example, an amorphous carbon layer that
further includes hydrogen, nitrogen, or the like.

[0042]The dependence of magnetic coercivity on the thickness of exchange
break layer 44 may have a `V` shape, as shown in FIGS. 3 and 4.
Coercivity of recording layer 40 may decrease when exchange break layer
44 is added between the hard and soft granular layers 42 and 46 and
reaches a minimum, after which coercivity of recording layer 40 starts
increasing. The coercivity increase occurs when the hard and soft
granular layers 42 and 46 are overly vertical exchange-decoupled, and
once hard and soft granular layers 42 and 46 are substantially fully
vertical exchange-decoupled, the coercivity of the composite structure
approaches the coercivity of the hard granular layer 42, which is higher.
The magnetic recording layer 40 with the exchange break layer 44 which
corresponds to the bottom of the `V` curve shows the greatest deviation
from the Stoner-Wohlfarth curve, i.e., the magnetic recording layer 40
demonstrates the most non-coherent magnetic orientation switching of the
tested samples.

[0043]Composite magnetic recording layers as described herein may provide
improved write-ability (e.g., magnetic coercivity of recording layer 40
is decreased) compared to some magnetic recording media of similar
magnetic stability (KuV/kT). Most importantly, vertical exchange
coupling, as utilized in magnetic recording layer 40 of the current
disclosure, may not increase the in-plane intra-granular exchange
interaction (i.e., lateral exchange coupling); thus, write-ability of
recording layer 40 may be decoupled from in-plane magnetic exchange
coupling in the currently described magnetic recording layer 40.

[0044]Exchange break layer 44 can vary in composition, from weakly
magnetic to non-magnetic. In embodiments in which exchange break layer 44
consists essentially of or consists of ruthenium, the minimum of the `V`
shape curve may be obtained for an exchange break layer 44 having a
thickness of less than 3 Å, as will be described below with reference
to FIGS. 4 and 5. In some examples, break layer 44 may consist
essentially of or consist of ruthenium. In the context of the present
application, "consists essentially of" means that a structure includes
substantially only the component listed, but may include small amount of
impurities present in commercially available sources of the component, or
relatively small amounts of components from adjacent structures or layers
which have diffused into the structure during manufacture, processing, or
use. In case of an exchange break layer 44 that comprises ruthenium and
cobalt, the maximum decrease in coercivity may be obtained for a
thickness between 10 Å and 15 Å (see curve 74 in FIGS. 4 and 5
below). An exchange break layer 44 comprising a thickness between
approximately 1 Å and approximately 2 Å may be advantageous, even
though such a break layer 44 may lead to manufacturing challenges. A thin
exchange break layer 44 allows a ratio of the thickness of hard granular
layer 42 in the thickness of recording layer 40 to be increased,
increasing the magnetic anisotropy energy of magnetic recording layer 40.

[0045]Magnetic recording layer 40 may still include CGC layer 48 on top of
soft granular layer 46 to reduce the slope of the MH loop by the addition
of lateral (in-plane) magnetic exchange interaction. However, since
write-ability is sufficiently addressed by the ECC effects between soft
granular layer 46 and hard granular 42, a thickness of CGC layer 48 can
be reduced. Reduction of the thickness of CGC layer 48 may reduce lateral
exchange coupling among adjacent grains of magnetic recording layer 40,
which, in turn, may reduce clustering of magnetic orientation of adjacent
grains.

[0046]CGC layer 48 may comprise, for example, CoCrPtBZ, where Z is a metal
or rare earth element dopant, such as Ru, W, Nb, or the like. In some
embodiments, CGC layer 48 may have a thickness of approximately 90 Å.
In some embodiments, CGC layer 48 may include a small amount of an oxide,
such as SiOx, TiOx, TaOx, WON, NbOx, CrOx,
CoOx, or the like. In other embodiments, CGC layer 48 may not
include an oxide.

[0048]In some embodiments, the magnetic anisotropy values of the three
magnetic layers (hard granular layer 42, soft granular layer 46, and CGC
layer 48) may decrease from the hard granular layer 42 to CGC layer 48.
Thus, hard granular layer 42 may have the highest magnetic anisotropy,
soft granular layer 46 may have an intermediate magnetic anisotropy, and
CGC layer 48 may have the lowest magnetic anisotropy. The actual magnetic
anisotropy values used in the three layers and the thickness of break
layer 44 may be selected such that the resulting magnetic recording layer
40 matches the given head field, e.g., is writeable at a magnetic field
that magnetic recording and read head 22 (FIG. 1) is able to produce. In
some embodiments, the magnetic anisotropy value of hard granular layer 42
may be between approximately 15 kOe and approximately 35 kOe, the
magnetic anisotropy value of soft granular layer 46 may be between
approximately 4 kOe and approximately 15 kOe, and the magnetic anisotropy
value of CGC layer 48 may be between approximately 6 kOe and
approximately 20 kOe.

[0049]Although recording layer 40 may have graded magnetic anisotropy
values, in that the value of the magnetic anisotropy energy of the
magnetic layers in recording layer 40 decreases monotonically from the
bottom to the top of the recording layer 40, other constraints may limit
the choice of materials for CGC layer 48. For example, mechanical
strength of the film may require a CGC layer 48 whose magnetic anisotropy
value is relatively high (e.g., higher than the anisotropy of soft
granular layer 46 but lower than the anisotropy of hard granular layer
42). In this case, soft granular layer 46, of low anisotropy, is
sandwiched between a hard granular layer 42, of high anisotropy, and a
continuous layer 48, of a somewhat higher anisotropy than soft granular
layer 46. In such an embodiment, the magnetization orientation of soft
granular layer 46 may be `pinned` to its neighbors' magnetization
orientation, and the magnetization orientation of soft granular layer 46
cannot rotate incoherently; the strength of the ECC effect may be reduced
or extinguished.

[0050]In some embodiments, as shown in FIG. 3, a recoding medium 60 may
include a recording layer 62 that has a hard granular layer 42, a first
exchange break layer 44 formed on hard granular layer 42, a soft granular
layer 46 formed on first exchange break layer 44, a second exchange break
layer 64 formed on soft granular layer 46, and a CGC layer 48 formed on
second exchange break layer 64. Second exchange break layer 64 separates
soft granular layer 46 and CGC layer 48 so that the low anisotropy of
soft granular layer 46 is not averaged with the magnetic anisotropy of
CGC layer 48, which may be higher than the magnetic anisotropy of soft
granular layer 46. This may increase the contrast in magnetic anisotropy
values between soft granular layer 46 and hard granular layer 44 compared
to a recording layer having a CGC layer 48 immediately adjacent to soft
granular layer 46. An increased contrast in magnetic anisotropy may
enhance the ECC effect.

[0051]In some embodiments, second exchange break layer 64 may comprise
ruthenium or a ruthenium alloy. In some embodiments, second exchange
break layer 64 may consist of or consist essentially of ruthenium. In
other embodiments, second exchange break layer 64 may include
cobalt-chromium-based non- or weakly-magnetic alloy, such as, for
example, a CoCr alloy, a CoRu alloy, or a CoCrRu alloy. Second exchange
break layer 64 may optionally include a non-magnetic oxide, such as, for
example, SiO2, TiO2CoO, Cr2O3, Ta2O5, or
the like. A second exchange break layer 64 including a non-magnetic oxide
may facilitate subsequent deposition of soft granular layer 46.

[0052]By introducing exchange break layer 44 between the hard granular
layer 42 at the bottom of the recording layer 40 and the layers on top of
hard granular layer 42 (which have relatively lower anisotropy than hard
granular layer 42) recording layer 40 may become easier to write (i.e.,
have a lower effective coercivity). The increased ease of recording data
to magnetic recording layer 40 may be achieved through the ECC effect, in
which the magnetically softer layers (e.g., CGC layer 48 and soft
granular layer 46) at the top of recording layer 40 begin to switch
magnetic orientations before hard granular layer 42 begins to switch
magnetic orientations when a recording field is applied. The softer
layers then exercise a magnetic torque on the hard granular layer 42,
thus reducing the effective coercivity of magnetic recording layer 40.
The reduction of the effective coercivity with thickness of break layer
44 is shown in FIGS. 4 and 5.

[0053]The strongest reduction in coercivity is observed when `Non-Co
alloy` is used for exchange break layer 44 (exchange break layer 44
consists of Ruthenium; curve 72 in FIGS. 4 and 5), where remnant
coercivity decreases to about 50% of the value when no exchange break
layer 44 is present. For comparison, when other exchange break layers 44
are used, with various Cobalt-containing compositions, the maximum
coercivity reduction is about 20% compared to the coercivity when no
exchange break layer 44 is present (the sample represented by curve 76 in
FIGS. 4 and 5 comprises a CoCrPtBCu alloy, the sample represented by
curve 74 in FIGS. 4 and 5 comprises a CoCrRu oxide alloy). Similar to
described above with respect to FIG. 2, each of the samples represented
in FIGS. 4 and 5 included a hard granular layer 42 that included a CoCrPt
alloy, at least one oxide, and a dopant element, such as Ru, W, Nb, or
the like. A thickness of hard granular layer 42 in each of the samples
was between approximately 50 Å and approximately 150 Å. Each of
the samples represented by curves 72, 74, 76 in FIGS. 4 and 5 also
included a soft granular layer 46 that included a CoCrPt alloy, at least
one oxide, and a dopant element, such as Ru, W, Nb, or the like. A
thickness of soft granular layer 46 was between approximately 20 Å
and approximately 100 Å. Additionally, each of the samples included a
CGC layer 48 comprising a CoCrPtB alloy doped with at least one of Ru, W,
Nb. A thickness of CGC layer 48 was between approximately 20 Å and
approximately 150 Å.

[0054]After exchange break layer 44 reaches a certain thickness (e.g.,
about 3 a.u. for curve 72, about 15 a.u. for curve 74, about 30 a.u. for
curve 76), the vertical magnetic exchange coupling between the top soft
layers (soft granular layer 46 and CGC layer 48) and hard granular layer
42 begins to decrease, and the ECC effect decreases. In other words, the
remnant coercivity of hard layer 42 begins to have a larger contribution
to the write coercivity of magnetic recording layer 40 for the purposes
of recording data to magnetic recording layer 40, because the soft layers
46 and 48 have relatively low coercivity by themselves and contribute to
less to the remnant coercivity of recording layer 40. Accordingly, the
remnant coercivity of recording layer 40 as a whole increases, and the
curves 72, 74, 76 have a `V` shape.

[0055]The ECC effect is based on the non-coherent reversal of the hard
granular layer 42 and soft layers (soft granular layer 46 and CGC layer
48): under an external magnetic field of sufficient strength, the soft
layers 46 and 48 begin to switch magnetic orientations first, followed by
switching of the magnetic orientation of hard granular layer 42. This
behavior is significantly different from that of CGC media, where all
magnetic layers in the recording layer switch magnetic orientations
coherently, substantially simultaneously. The deviation from coherent
magnetic orientation switching due to the ECC effect can be evaluated by
measuring the remnant coercivity dependence on the angle of the applied
magnetic field relative to the easy axis of the magnetic grains, examples
of which are shown in FIGS. 6 and 7. When switching of magnetic
orientation of the layers in magnetic recording layer 40 is coherent, as
for CGC media, the magnetic field necessary to switch the magnetic
orientation of grains in magnetic recording layer 40 is maximum when the
external field is parallel to the easy axis of the grains (0 degrees in
FIGS. 6 and 7), and minimum when the applied field angle is 45 degrees
(shown by curve 86). In theory, this is described by the Stoner-Wohlfarth
curve, and the minimum coercivity should be equal to 0.5 of the maximum
coercivity. For CGC media, FIGS. 6 and 7 illustrate the minimum
coercivity (at 45 degrees) is about 0.75 of the maximum coercivity (at 0
deg); the difference between the observed coercivity decrease and the
theoretical coercivity decrease is due to the dispersion in the
orientations of the easy axes of the grains.

[0056]In ECC media, as described herein, the use of exchange break layer
44 between hard granular layer 42 and soft granular layer 46 results in
deviation from the Stoner-Wohlfarth curve: remnant coercivity is less
dependent on the applied field angle at small angles. This is indicated
by the relative flatness of the remnant coercivity versus applied field
angle curves 82 and 84 illustrated in FIGS. 6 and 7. For example, curves
82 and 84 for recording layers including a break layer show less
dependence of remnant coercivity on the applied field angles for applied
field angles of less than approximately 60 degrees than the curve 86 for
a CGC recording layer. FIGS. 6 and 7 also illustrate that the remnant
coercivity of the recording layers including a break layer 44 increases
considerably when the field is applied at 90 degrees (in the plane of the
recording layer 40; see curves 82 and 84). This behavior was predicted by
theory for ECC recording layers and supports the incoherent magnetic
orientation reversal of a recording layer 40 including a break layer 44
between a hard granular layer 42 and a soft granular layer 44.

[0057]Magnetic recording media with exchange break layer 44 may offer
increased write-ability (lower effective coercivity) compared to CGC
media, while maintaining acceptable thermal stability. FIG. 8 shows that
the energy barrier (KuV/kT) is not substantially decreased by the
introduction of an exchange break layer 44 consisting essentially of
ruthenium between hard granular layer 42 and soft granular layer 46 until
the thickness of exchange break layer 44 is greater than about 2 a.u.
Accordingly, an exchange break layer 44 consisting essentially of
ruthenium and having a thickness between 0 and about 2 a.u. may be used
in recording layer 40, as magnetization orientation switching due to
thermal fluctuations is not a significant concern.

[0058]Each of the samples represented in FIG. 8 included a hard granular
layer 42 that included a CoCrPt alloy, at least one oxide, and a dopant
element, such as Ru, W, Nb, or the like. A thickness of hard granular
layer 42 in each of the samples was between approximately 50 Å and
approximately 150 Å. Each of the samples represented in FIG. 8 also
included a soft granular layer 46 that comprised a CoCrPt alloy, at least
one oxide, and a dopant element, such as Ru, W, Nb, or the like. A
thickness of soft granular layer 46 was between approximately 20 Å
and approximately 100 Å. Additionally, each of the samples included a
CGC layer 48 comprising a CoCrPtB alloy doped with at least one of Ru, W,
Nb. A thickness of CGC layer 48 was between approximately 20 Å and
approximately 150 Å.

[0059]A desirable thickness of the exchange break layer 44 for a
particular recording layer 40 may be determined from measurement of a
switching field distribution (SFD). As FIG. 9 shows, the SFD improves
slightly when the vertical exchange coupling between the hard granular
layer 42 and soft granular layer 46 improves (thickness of between 0 and
about 2 a.u. for an exchange break layer 44 consisting essentially of
ruthenium). As the thickness of exchange break layer 44 increases
further, the vertical exchange coupling between hard granular layer 42
and soft granular layer 46 begins to decrease and the ensemble of grains
splits into two distributions, one distribution formed by grains in hard
granular layer 42, a second distribution formed by grains in soft
granular layer 46. When trying to fit this bi-modal distribution by a
single SFD, a large value is obtained. A sudden `jump` in SFD indicates
such decoupling, and occurs at about 2 a.u. for an exchange break layer
44 consisting essentially of ruthenium, as shown in FIG. 9.

[0060]Each of the samples represented in FIG. 9 included a hard granular
layer 42 that included a CoCrPt alloy, at least one oxide, and a dopant
element, such as Ru, W, Nb, or the like. A thickness of hard granular
layer 42 in each of the samples was approximately 90 Å. Each of the
samples represented in FIG. 9 also included a soft granular layer 46 that
comprised a CoCrPt alloy, at least one oxide, and a dopant element, such
as Ru, W, Nb, or the like. A thickness of soft granular layer 46 was
approximately 40 Å. Additionally, each of the samples included a CGC
layer 48 comprising a CoCrPtB alloy doped with at least one of Ru, W, Nb.
A thickness of CGC layer 48 was approximately 90 Å.

[0061]FIGS. 10 and 11 illustrate results of a comparison of the effect of
break layer thickness on two designs of a recording layer. Curve 94
illustrates results for a recording layer 40 having a hard granular layer
42/break layer 44/CGC layer 48 structure. Hard granular layer 42 included
a CoCrPt alloy, at least one oxide, and a dopant element, such as Ru, W,
Nb, or the like, and had a thickness of 90 Å. CGC layer 48 comprised
a CoCrPtB alloy doped with at least one of Ru, W, Nb, and had a thickness
of approximately 90 Å. The recording layer 40 represented by curve 94
does not include a soft granular layer 46. Curve 92 illustrates results
for a recording layer 40 having a hard granular layer 42/break layer
44/soft granular layer 46/CGC layer 48. Hard granular layer 42 included a
CoCrPt alloy, at least one oxide, and a dopant element, such as Ru, W,
Nb, or the like, and had a thickness of 90 Å. Soft granular layer 46
comprised a CoCrPt alloy, at least one oxide, and a dopant element, such
as Ru, W, Nb, or the like, and had a thickness of approximately 40 Å.
CGC layer 48 comprised a CoCrPtB alloy doped with at least one of Ru, W,
Nb, and had a thickness of approximately 90 Å.

[0062]FIGS. 10 and 11 show that a similar reduction of coercivity
(translating into easier recording of information to recording layer 40)
occurs at smaller thicknesses of exchange break layer 44 for curve 92,
i.e., when a soft granular layer 46, is present. The ECC effect appears
when the grains themselves are composite, in the sense that each grain
has a magnetically hard bottom vertically exchange coupled to a
magnetically soft top. The minimum of the remnant coercivity curve is
also greater in curve 94, when a soft granular layer 46 is not present,
meaning the reduction in coercivity is not as great (about 40% remnant
coercivity reduction instead of about 50% remnant coercivity reduction).

[0063]The write-ability improvement (accompanied by acceptable thermal
stability) offered by a recording layer 40 including an exchange break
layer 44 may enable better recording system performance in at least one
of at least two ways. First, narrower heads can be used to record data to
such a recording layer 40. While narrower heads may produce an applied
field of lower magnitude, recording layer 40 may still be write-able due
to the ECC effect produced by hard granular layer 42, exchange break
layer 44, and soft granular layer 44. Narrower heads may enable higher
areal densities by writing the data tracks closer together. As shown in
FIG. 12, ADC (areal density capability) shows that a recording layer 40
including an exchange break layer 44 with certain thicknesses (less than
approximately 2.5 a.u. for ruthenium) may provide better performance than
the reference, which does not include an exchange break layer.

[0064]Each of the samples represented in FIG. 9 included a hard granular
layer 42 that included a CoCrPt alloy, at least one oxide, and a dopant
element, such as Ru, W, Nb, or the like. A thickness of hard granular
layer 42 in each of the samples was approximately 90 Å. Each of the
samples represented in FIG. 9 also included a soft granular layer 46 that
comprised a CoCrPt alloy, at least one oxide, and a dopant element, such
as Ru, W, Nb, or the like. A thickness of soft granular layer 46 was
approximately 40 Å. Additionally, each of the samples included a CGC
layer 48 comprising a CoCrPtB alloy doped with at least one of Ru, W, Nb.
A thickness of CGC layer 48 was approximately 90 Å.

[0065]Second, the fact that the `Non-Co alloy` (ruthenium) exchange break
layer 44 consisting essentially of ruthenium may be extremely thin
relative to an exchange break layer 44 including a Co alloy may allow use
of a thicker hard granular layer 42 compared to a recording layer 40
including an exchange break layer 44 including a Co alloy. For example,
thickness of hard granular layer 42 ("HGL Thickness" in Table 1) can be
increased from 90 Å to 120 Å, and while maintaining the total
thickness of recording layer 40 below 200 Å. A thicker hard granular
layer 42 results in a higher thermal energy barrier (KuV) compared
to a thinner hard granular layer 42 of the same anisotropy. In this way,
a thicker hard granular layer 42 can improve erasure-related issues, such
as, for example, adjacent track interference, mechanical scratch
resistance, or the like. The following Table 1 shows three recording
layers with increasing thickness of hard granular layer 42, higher
KuV values (improved thermal stability), and other performance
metrics (Writability--more negative is better and SNR--higher is better)
substantially equal to the reference recording layer.

[0066]Although the embodiments described above include one exchange break
layer 44 or a first exchange break layer 44 and a second exchange break
layer 64, in some embodiments, a recording layer may include three or
more exchange break layers. For example, FIG. 13 illustrates a recording
layer 100 including a hard granular layer 102, a first exchange break
layer 104, an intermediate granular layer 106, a second exchange break
layer 108, a soft granular layer 110, a third exchange break layer 112,
and a CGC layer 114.

[0067]Hard granular layer 102 may be similar in composition and/or
thickness to hard granular layer 42. The magnetic anisotropy of hard
granular layer 102 may be oriented in a direction substantially
perpendicular to the plane of recording layer 100 (e.g., the easy axes of
grains in hard granular layer 102 may be substantially perpendicular to
the plane of recording layer 100). Hard granular layer 102 may comprise,
for example, a Co alloy. The Co alloy may include Co in combination with
at least one of Cr, Ni, Pt, Ta, B, Nb, O, Ti, Si, Mo, Cu, Ag, Ge, or Fe.
In some embodiments, hard granular layer 102 may include an Fe--Pt alloy,
a Sm--Co alloy, or the like. Hard granular layer 102 may include a
non-magnetic oxide, such as SiO2, TiO2CoO, Cr2O3,
Ta2O5, or the like, which separates the magnetic grains within
the hard granular layer 102 and reduces lateral magnetic coupling between
the grains in hard granular layer 102.

[0068]First exchange break layer 104 may be formed on hard granular layer
102, and may comprise ruthenium or a ruthenium alloy. As described above,
in some embodiments, first exchange break layer 104 may consist
essentially of or consist of ruthenium. A first exchange break layer 104
consisting essentially of ruthenium may provide similar vertical exchange
coupling between hard granular layer 102 and intermediate granular layer
106 at a lower thickness than a first exchange break layer 104 comprising
a ruthenium alloy. For example, a first exchange break layer 104
consisting essentially of ruthenium may provide desirable vertical
exchange coupling at a thickness less than approximately 3 Å. In
embodiments in which exchange break layer 104 comprises a ruthenium
alloy, first exchange break layer 104 may include, for example, a
CoxRu1-x alloy. A first exchange break layer 104 including a
ruthenium alloy may have a greater thickness, such as, for example,
between 0 Å and approximately 60 Å. In some embodiments, a first
exchange break layer 104 including a ruthenium alloy may have a thickness
between approximately 10 Å and approximately 30 Å. In addition to
Ru or a CoxRu1-x alloy, exchange break layer 104 may optionally
include a non-magnetic oxide, such as, for example, SiO2,
TiO2CoO, Cr2O3, Ta2O5, or the like. A first
exchange break layer 104 including a non-magnetic oxide may facilitate
subsequent deposition of intermediate granular layer 106.

[0069]Intermediate granular layer 106 is formed on first exchange break
layer 104 and may include a plurality of grains that have a magnetic
anisotropy oriented in a direction substantially perpendicular to the
plane of recording layer 100 (e.g., the easy axes of grains in
intermediate granular layer 106 may be substantially perpendicular to the
plane of recording layer 100). Intermediate granular layer 106 may
comprise, for example, a Co alloy. The Co alloy may include Co in
combination with at least one of Cr, Ni, Pt, Ta, B, Nb, O, Ti, Si, Mo,
Cu, Ag, Ge, or Fe. In some embodiments, intermediate granular layer 106
may include an Fe--Pt alloy, a Sm--Co alloy, or the like. Intermediate
granular layer 106 may include a non-magnetic oxide, such as SiO2,
TiO2CoO, Cr2O3, Ta2O5, or the like, which
separates the magnetic grains within the intermediate granular layer 106
and reduces lateral magnetic coupling between the grains in intermediate
granular layer 106.

[0070]Intermediate granular layer 106 may have a different composition
than hard granular layer 102. In some embodiments, the composition of
intermediate granular layer 106 results in intermediate granular layer
106 having a magnetic anisotropy value lower than that of hard granular
layer 102.

[0071]Second exchange break layer 108 is formed on intermediate granular
layer 106, and may comprise ruthenium or a ruthenium alloy. In some
embodiments, second exchange break layer 108 may include a similar
composition as first exchange break layer 104, while in other
embodiments, second exchange break layer 108 may include a different
composition than first exchange break layer 104. For example, in some
embodiments, second exchange break layer 108 may consist essentially of
or consist of ruthenium. A second exchange break layer 108 consisting
essentially of ruthenium may provide similar vertical exchange coupling
between intermediate granular layer 106 and soft granular layer 110 at a
lower thickness than a second exchange break layer 108 comprising a
ruthenium alloy. For example, a second exchange break layer 108
consisting essentially of ruthenium may provide desirable vertical
exchange coupling at a thickness less than approximately 3 Å. In
embodiments in which second exchange break layer 108 comprises a
ruthenium alloy, second exchange break layer 108 may include, for
example, a CoxRu1-x alloy. A second exchange break layer 108
including a ruthenium alloy may have a greater thickness, such as, for
example, between 0 Å and approximately 60 Å. In some embodiments,
a second exchange break layer 108 including a ruthenium alloy may have a
thickness between approximately 10 Å and approximately 30 Å. In
addition to Ru or a CoxRu1-x alloy, second exchange break layer
108 may optionally include a non-magnetic oxide, such as, for example,
SiO2, TiO2CoO, Cr2O3, Ta2O5, or the like. A
second exchange break layer 108 including a non-magnetic oxide may
facilitate subsequent deposition of soft granular layer 110.

[0072]Soft granular layer 110 is formed on second exchange break layer 108
and may include a plurality of grains that have a magnetic anisotropy
oriented in a direction substantially perpendicular to the plane of
recording layer 100 (e.g., the easy axes of grains in soft granular layer
110 may be substantially perpendicular to the plane of recording layer
100). In some embodiments, soft granular layer 110 comprises a Co alloy
including Co in combination with at least one of Cr, Ni, Pt, Ta, B, Nb,
O, Ti, Si, Mo, Cu, Ag, Ge, or Fe. In other embodiments, soft granular
layer 110 includes an Fe--Pt alloy, a Sm--Co alloy, or the like. Soft
granular layer 110 may include a non-magnetic oxide, such as SiO2,
TiO2CoO, Cr2O3, Ta2O5, or the like, which
separates the magnetic grains within the soft granular layer 110 and
reduces lateral magnetic coupling between the grains in soft granular
layer 110.

[0073]Soft granular layer 110 may have a different composition than hard
granular layer 102 and/or intermediate granular layer 106. In some
embodiments, the composition of soft granular layer 110 results in soft
granular layer 110 having a magnetic anisotropy value lower than those of
intermediate granular layer 106 and hard granular layer 102.

[0074]Third exchange break layer 112 is formed on soft granular layer 110,
and may comprise ruthenium or a ruthenium alloy, similar to first and
second exchange break layer 104 and 108. In some embodiments, third
exchange break layer 112 may include a similar composition as first
exchange break layer 104 and/or second exchange break layer 108, while in
other embodiments, third exchange break layer 112 may include a different
composition than first exchange break layer 104 and second exchange break
layer 108. For example, third exchange break layer 112 may consist
essentially of or consist of ruthenium, or may comprise a ruthenium
alloy, e.g., CoxRu1-x. In addition to Ru or a
CoxRu1-x alloy, third exchange break layer 112 may optionally
include a non-magnetic oxide, such as, for example, SiO2,
TiO2CoO, Cr2O3, Ta2O5, or the like.

[0075]CGC layer 114 is formed on top of third exchange break layer 112, in
order to reduce the slope of the MH loop by the addition of lateral
(in-plane) magnetic exchange interaction in recording layer 100. However,
since write-ability is sufficiently addressed by the ECC effects between
soft granular layer 110, intermediate granular layer 106, and hard
granular layer 102, a thickness of CGC layer 114 can be reduced.
Reduction of the thickness of CGC layer 114 may reduce lateral exchange
coupling among adjacent grains of magnetic recording layer 100, which, in
turn, may reduce clustering of magnetic orientation of adjacent grains.

[0076]In general, the concept of exchange break layers and a plurality of
granular magnetic layers having a magnetic anisotropy gradient may be
extended to an arbitrary number of layers. For example, as shown in FIG.
14, a magnetic recording layer 120 may include (2n-1) layers, including n
magnetic layers alternating with n-1 exchange break layers, where n is an
integer greater than or equal to 3. In particular, FIG. 14 illustrates a
first magnetic layer 122, which may be a granular magnetic layer with
relatively high magnetic anisotropy (e.g., the highest magnetic
anisotropy of any magnetic layer in recording layer 120). The magnetic
anisotropy of first magnetic layer 122 is oriented in a direction
substantially perpendicular to the plane of recording layer 120 (e.g.,
the easy axes of grains in first magnetic layer 122 may be substantially
perpendicular to the plane of recording layer 120). First magnetic layer
122 may comprise a Co alloy, an Fe--Pt alloy, a Sm--Co alloy, or the
like, and may include a non-magnetic oxide, such as, SiO2,
TiO2CoO, Cr2O3, Ta2O5, or the like, as described
above.

[0077]First exchange break layer 124 is formed on first magnetic layer
122. First exchange break layer 124 may comprise ruthenium or a ruthenium
alloy. In some embodiments, first exchange break layer 124 may consist
essentially of or consist of ruthenium, while in other embodiments, first
exchange break layer 124 may comprise a ruthenium alloy, e.g.,
CoxRu1-x. In addition to Ru or a CoxRu1-x alloy,
first exchange break layer 124 may optionally include a non-magnetic
oxide, such as, for example, SiO2, TiO2CoO, Cr2O3,
Ta2O5, or the like.

[0078]Second magnetic layer 126 is formed on first exchange break layer
124, and may be a granular magnetic layer with magnetic anisotropy that
is relatively high, but less than the magnetic anisotropy of first
magnetic layer 122. The magnetic anisotropy of second magnetic layer 126
is oriented in a direction substantially perpendicular to the plane of
recording layer 120 (e.g., the easy axes of grains in second magnetic
layer 126 may be substantially perpendicular to the plane of recording
layer 120). Second magnetic layer 126 may comprise a Co alloy, an Fe--Pt
alloy, a Sm--Co alloy, or the like, and may include a non-magnetic oxide,
such as, SiO2, TiO2CoO, Cr2O3, Ta2O5, or
the like, as described above. The composition of second magnetic layer
126 may be different than the composition of first magnetic layer 122,
such that second magnetic layer 126 has a lower magnetic anisotropy value
that first magnetic layer 122. For example, second magnetic layer 126 may
include similar components as first magnetic layer 122, but in different
proportions.

[0079]Recording layer 120 may include an arbitrary of magnetic layers and
exchange break layers in an alternating pattern. Each subsequent magnetic
layer may have a lower magnetic anisotropy than the magnetic layer before
it. For example, magnetic layer n-2 (not shown) may have a lower magnetic
anisotropy than magnetic layer n-3 (not shown). Exchange break layer n-1
128 is formed on magnetic layer n-1. Exchange break layer n-1 128 may
comprise ruthenium or a ruthenium alloy, and may have a similar
composition to first exchange break layer 124 or a different composition
than first exchange break layer 124. In some embodiments, exchange break
layer n-1 128 may consist essentially of or consist of ruthenium, while
in other embodiments, exchange break layer n-1 128 may comprise a
ruthenium alloy, e.g., CoxRu1-x. In addition to Ru or a
CoxRu1-x alloy, exchange break layer n-1 128 may optionally
include a non-magnetic oxide, such as, for example, SiO2, TiO2
CoO, Cr2O3, Ta2O5, or the like.

[0080]Magnetic layer n 130 is formed on exchange break layer n-1 128, and
in some embodiments may be a granular magnetic layer with magnetic
anisotropy that is relatively low, e.g., lower than the magnetic
anisotropy of any other of the magnetic layers in recording layer 120. In
embodiments in which magnetic layer n is a granular magnetic layer, the
magnetic anisotropy of magnetic layer n 130 is oriented in a direction
substantially perpendicular to the plane of recording layer 120 (e.g.,
the easy axes of grains in magnetic layer n 130 may be substantially
perpendicular to the plane of recording layer 120). Magnetic layer n 130
may comprise a Co alloy, an Fe--Pt alloy, a Sm--Co alloy, or the like,
and may include a non-magnetic oxide, such as, SiO2, TiO2CoO,
Cr2O3, Ta2O5, or the like, as described above. The
composition of magnetic layer n 130 may be different than the composition
of first magnetic layer 122 and/or second magnetic layer 126, such that
magnetic layer n 130 has a lower magnetic anisotropy value than first
magnetic layer 122 and second magnetic layer 126. For example, magnetic
layer n 130 may include similar components as first magnetic layer 122
and/or second magnetic layer 126, but in different proportions. While not
shown in FIG. 14, in some embodiments in which magnetic layer n 130 is a
granular magnetic layer, recording layer 120 may include a CGC layer
formed on magnetic layer n. The CGC layer may be similar to those
described above with reference to FIGS. 2, 3, and 13.

[0081]In some embodiments, magnetic layer n 130 may comprise a CGC layer,
similar to CGC layer 48 described with reference to FIGS. 2 and 3 or CGC
layer 114 described with reference to FIG. 13.

[0082]An increased number of magnetic layers and exchange break layers in
recording layer 120 may provide improved recording and/or read
performance compared to a recording layer with fewer magnetic layers
and/or exchange break layers, as shown in FIG. 15. FIG. 15 is a plot of
the normalized coercivity, Hc, of a magnetic recording layer as a
function of the angle of an applied magnetic field. FIG. 15 illustrates
experimental data obtained for a recording layer 120 including seven
layers, of which four are magnetic layers and three are exchange break
layers, and for a recording layer 120 including five layers, of which
three are magnetic layers and two are exchange break layers. The angular
dependence of the coercivity for the recording layer 120 including seven
layers is decreased compared to the angular dependence of the coercivity
for the recording layer including five layers. This, along with the
improved bit error rate and improved ADC shown in Table 2, indicates that
a seven layer recording layer may provide improved performance compared
to a five layer recording layer.